Golf ball core and cover layers are typically constructed with polymer compositions including, for example, polybutadiene rubber, polyurethanes, polyamides, ionomers, and blends thereof. Ionomers, particularly highly neutralized ionomers, are a preferred group of polymers for golf ball layers because of their resilience, durability, and wide range of hardness values. However, conventional highly neutralized ionomers are hydrophilic, due to the highly hydrophilic nature of the cation sources traditionally used to neutralize the ionomers, e.g., magnesium and magnesium salts of fatty acids. As a result of their hydrophilic nature, conventional highly neutralized ionomers can absorb a significant amount of moisture, e.g., 2,000 to 10,000 parts per million (ppm), which can result in processing difficulties, such as creating voids in the part during an injection molding process, and a reduction in golf ball performance, such as decreased coefficient of restitution and stiffness due to the plasticization of ionic aggregates by water molecules.
Therefore, a desire remains for compositions containing highly neutralized acid polymers having improved moisture vapor transmission properties. The present invention describes such compositions and the use thereof in a variety of golf ball core and cover layers.